1. Field of the Invention
The present invention relates to a piping arrangement for swing type hydraulic excavators.
2. Description of the Related Art
Conventionally, employed frequently for small-sized hydraulic excavators used for urban type public works are swing type hydraulic excavators comprising an implement having a boom, an arm, a bucket, and the like and mounted on a forward end of an upper swivel body through a swing bracket, which is mounted to be able to transversely swing (referred below to as swing), to be able to vertically swing, and making combined use of swiveling of the upper swivel body and swing of the implement to make the implement offset from a lower swivel body to enable sewer excavation. Further, an implement comprises a boom cylinder, an arm cylinder, a bucket cylinder, and many actuators such as hydraulic cylinders for various attachments, or the like, and pipes for feeding of oil thereto are large in number.
Accordingly, in piping design to extend these many pipes from respective main control valves on a swivel frame through a boom to arrange them on respective actuators, there is needed a careful consideration taking account of maintenance, beautiful view, or the like, not to mention breakage of the pipes, and prevention of a trouble with oil leakage. In particular, it is one of very important things to arrange lengths of hose around the swing bracket; which needs two operations, that is, vertical swing and transverse swing of the implement, while ensuring reliability on the lengths of hose.
Conventionally, means for arranging a group of pipes around a swing bracket in a swing type hydraulic excavator is disclosed in, for example, pages 2 to 4 and FIGS. 5 and 6 in Patent Document 1 (JP-A-2000-96610) to be known. FIG. 6 in the Patent Document is a perspective view showing a piping for a boom cylinder in the swing type hydraulic excavator described in Patent Document 1.
As shown in FIG. 6, a swing bracket 109 swingable about a vertical shaft is pivotally mounted on a front end of a swivel slide 104 (corresponding to a swivel frame in the invention, and referred below to as a swivel frame 104), and a root portion 119 of a boom structure 113 (referred below to as a boom 113) is mounted on the swing bracket 109 through a transverse pivot 120 to be movable vertically. The swing bracket 109 is pivotally mounted by the transverse pivot 120 in a state, in which the swing bracket is interposed by the root portion 119 of the boom 113, to define in front of the transverse pivot 120 a space 122 surrounded by the root portion 119. A major part of a hose group 123 for a working oil passing through an interior of the swing bracket 109 passes through the space 122 upward from below and reaches an upper surface of the boom 113.
As shown in FIG. 6, lengths of hydraulic hose 123A for a boom cylinder 116 extend from the swivel frame 104 without passage through the interior of the swing bracket 109 to directly pass by a side of the swing bracket 109 via a holder 123B to be connected to respective piping ports of the boom cylinder 116.
Also, for example, Patent Document 2 (JP-A-2000-230251, pages 3 to 4, FIGS. 2 and 5) describes a construction of an implement associated with piping of lengths of hydraulic hose for driving of the implement around a swing bracket of a conventional swing type hydraulic excavator. FIG. 7 is a side view showing a construction of an implement around a swing bracket and piping of lengths of hydraulic hose for an implement described in Patent Document 2. In FIG. 7, a swivel working vehicle comprises a boom 206 mounted to a swivel body 202, which is constructed to be able to swivel, through a boom bracket 212 (corresponding to a swing bracket in the invention, and referred below to as a swing bracket 212) to be able to swing vertically, and an implement having an arm (not shown) mounted on the boom 206 to be able to swing vertically. A hose guide 214 is provided fixedly on an upper end of a swing pin 213 extending vertically through the swivel body 202 and the swing bracket 212 and connecting the both together to enable the same to swing left and right. The hose guide 214 guides lengths of hydraulic hose for the implement, extended from the swivel body 202, and a major part of the lengths of hydraulic hose is arranged inside the boom 206.
Further, among the lengths of hydraulic hose, lengths of hose 223 for the boom cylinder are extended from a swivel frame upper plate 202a to pass through an interior of the swing bracket 212 to be connected to a boom cylinder 211 as shown in FIG. 7. That is, the lengths of hose 223 for the boom cylinder extend above the swivel frame upper plate 202a and lowers via a downwardly opening guide hole 212c of a boom support 206a on the swing bracket 212. The lengths of hose 223 extend below a cylinder support 212b of the boom cylinder 211 and goes around the cylinder support 212b to extend from an interior of the swing bracket 212 to be connected to respective piping ports of the boom cylinder 211 disposed above.
However, the conventional technique described above involves the following problems. In the conventional technique described in Patent Document 1, lengths of hydraulic hose 123A for the boom cylinder and extending from the swivel frame 104 pass by the side of the swing bracket 109 to be arranged. Hereupon, in order to ensure a space for expansion of the lengths of hydraulic hose caused when the boom 113 swings, there is a need for a spacing between the swivel frame 104 and the swing bracket 109, so that the whole machine is made large in size. Also, since the lengths of hydraulic hose 123A are exposed to outside at many portions thereof, there is increased a fear of damage caused by fly stone and impinging matters. Further, since the lengths of hydraulic hose 123A cover the side of the swing bracket 109, a beautiful sight around the swing bracket 109 is injured.
Also, the conventional technique described in Patent Document 2 involves the following problems. The piping arrangement of the lengths of hose 223 for the boom cylinder, which meander inside the swing bracket 212 to reach the boom cylinder 211, requires an exclusive piping passage inside the swing bracket 212, and therefore the swing bracket 212 is made complicate in structure, large in size, and expensive. Also, the lengths of hose 223 for the boom cylinder project forwardly of a forward most portion of the swing bracket 212, and so there is a fear of generation of damage caused by fly stone, impinging matters, and the like.